It is a fast and portable binary serializer designed to be easily used on your existing code with minimal changes on a wide range of .NET platforms. With AqlaSerializer you can store objects as a small in size binary data (far smaller than xml). And it's more CPU effective than BinaryFormatter and other core .NET serializers (which could be unavailable on your target platform).
Basically this is a fork of well known data serializer protobuf-net.
AqlaSerializer is an object serializer, it's primary goal is to support important .NET features like nested collections, references, etc. See also comparison with protobuf-net page. And it still supports Google Protocol Buffers format in compatibility mode.
It is a free open source project in which you can participiate.
See also wiki.
See also License.txt.