Use ArcGIS Server REST resources without an official SDK.
Can I help to improve it and/or fix bugs?
Absolutely! Please feel free to raise issues, fork the source code, send pull requests, etc.
No pull request is too small. Even whitespace fixes are appreciated. Before you contribute anything make sure you read CONTRIBUTING.
If you have NuGet installed, the easiest way to get started is to install via NuGet:
PM> Install-Package ArcGIS.PCL
On Xamarin you can add the ArcGIS.PCL component from the component store or use NuGet since it is now supported in Xamarin Studio.
Of course you can also get the code from this site.
What do the version numbers mean?
ArcGIS.PCL uses Semantic Versioning.