diff --git a/apps/grepo_base/backends/__init__.py b/apps/grepo_base/backends/__init__.py
index bde31ea..47196cf 100644
--- a/apps/grepo_base/backends/__init__.py
+++ b/apps/grepo_base/backends/__init__.py
@@ -15,11 +15,6 @@
 
        Updates a given :class:`~grepo_base.models.Repository` object,
        **without** saving it to the database.
-
-    .. function:: needs_update(repository)
-
-       Returns ``True`` if a given :class:`~grepo_base.models.Repository`
-       instance needs to be updated and ``False`` otherwise.
 """
 
 from django.conf import settings
diff --git a/apps/grepo_base/backends/github.py b/apps/grepo_base/backends/github.py
index 0c26ba8..072b816 100644
--- a/apps/grepo_base/backends/github.py
+++ b/apps/grepo_base/backends/github.py
@@ -3,57 +3,76 @@
     grepo_base.github
     ~~~~~~~~~~~~~~~~~
 
+    Github.com backend for `grepo`.
 """
-from datetime import datetime
-
-from json import loads
-from itertools import count
+import itertools
 from httplib import HTTPConnection
+from datetime import datetime
 
 from django.conf import settings
+from django.utils import simplejson as json
+
+from grepo_base.models import Repository, Language
 
-from grepo_base.models import Repository
 
 #: Github api search path
 SEARCH_PATH = "/api/v2/json/repos/search/language:{lang}?start_page={page}"
 #: Github host, used for httplib for connect to api
 GITHUB = "github.com"
-#: List of languages that we will be processed
-LANGUAGES = [lang[0].upper() + lang[1:] for lang in settings.GREPO_LANGUAGES]
 
 
-def get_page(lang, page):
+def fetch(language, page):
     connection = HTTPConnection(GITHUB)
-    connection.request("GET", SEARCH_PATH.format(lang=lang, page=page))
+    connection.request("GET", SEARCH_PATH.format(lang=language, page=page))
     response = connection.getresponse()
-    return response
+    foo = response.read()
+    return foo
+
+
+def list():
+    """Yields all repositories one by one."""
+    for language in Language.objects.all():
+        for page in itertools.count(1):
+            data = fetch(language.name, page)
+            repositories = json.loads(data)["repositories"]
+
+            if not repositories:
+                break
+
+            for repository in repositories:
+                if not repository["language"]:
+                    continue
 
+                # Note: `source` and `language` field should be handled
+                # by the caller.
+                yield {
+                    "url": repository["url"],
+                    "name": repository["name"],
+                    "language": repository["language"],
+                    "summary": repository["description"],
+                    "score": calculate_repository_score(repository),
+                    "updated_at": datetime.utcnow(),
+                    "created_at": datetime.utcnow()
+                }
 
-def fetch_by_lang(lang):
-    for page in count(1):
-        page = get_page(lang, page)
-        repositories = loads(page.read())["repositories"]
-        if not repositories:
-            break
-        for repository in repositories:
-            yield repository
 
+def update(repository):
+    return repository  # A simple pass-through for now.
 
-def fetch_repositories():
-    for lang in LANGUAGES:
-        for repository in fetch_by_lang(lang):
-            yield repository
 
+def calculate_repository_score(data):
+    """Calculates and returns Grepo-score for a given repository.
 
-def save_repository(repository):
-    obj = Repository(url=repository["url"], name=repository["name"],
-                     source=0,
-                     language=LANGUAGES.index(repository["language"]),
-                     summary=repository.get("description"),
-                     updated_at=datetime.utcnow(), created_at=datetime.utcnow())
-    obj.save()
+    .. todo:: query for pull requests and add them to the exponent
+              argument.
+    """
+    parse = lambda d: datetime.strptime(d, "%Y/%m/%dT %H:%M:%S %z")
 
+    data.update(
+        created_at=parse(data["created_at"]),
+        pushed_at=parse(data["pushed_at"])
+    )
 
-def rescan_github():
-    for repository in fetch_repositories():
-        save_repository(repository)
+    return (data["created_at"] - data["pushed_at"]) * math.exp(
+        1 / (data["open_issues"] + data["watchers"] / data["forks"])
+    )
diff --git a/apps/grepo_base/backends/lp.py b/apps/grepo_base/backends/lp.py
index 68d96ba..99510f7 100644
--- a/apps/grepo_base/backends/lp.py
+++ b/apps/grepo_base/backends/lp.py
@@ -55,7 +55,7 @@ def get_repos():
         yield get_project_info(project.name, language_list)
 
 def get_project_info(name, language_list):
-    project = launchpad.projects[name]    
+    project = launchpad.projects[name]
     info = {}
     info['name'] = name
     info['created_at'] = project.date_created
@@ -102,7 +102,7 @@ def get_project_languages(language_string):
         languages = language_string.split(r'/')
     if len(languages) == 1:
         languages = language_string.split(r' ')
-        
+
     language_list = []
     for l in languages:
         language = guess_language(l)
@@ -110,4 +110,3 @@ def get_project_languages(language_string):
             language_list.append(language)
 
     return set(language_list)
-
diff --git a/apps/grepo_base/models.py b/apps/grepo_base/models.py
index f517b00..038e368 100644
--- a/apps/grepo_base/models.py
+++ b/apps/grepo_base/models.py
@@ -64,8 +64,3 @@ def __unicode__(self):
     def save(self):
         self.updated_at = datetime.now()
         super(Repository, self).save()
-
-
-def calculate_grepo_score():
-    """Returns `grepo` score for a bunch of repository metadata."""
-    return 0