There is no official roadmap, yet lots of ideas are floating around.
Apart from maintaining and improving the current codebase and adding new bridges, there are others things we are considering.
One thing that is already in the works is a full-featured guitar effects processor using LV2 plugins called FreeADSP.
Another is to write a LV2 plugin server (and a correspnding bridge) which can be used to bridge non-native plugins (for example, x86 plugins on x86-64 platforms or Windows plugins on non-Windows platforms through Wine).
Then, we are also working on a collection of guitar effects plugins implemented with Permafrost called zanga-plugins.
Long term plans include investigating the possibility of developing a POSIX shell only-based build system (Tiano), some LV2 extensions and other stuff which is not yet worth mentioning.
At the moment NASPRO should work on all POSIX-compilant OSes, but anyway it's been properly tested only on Linux.
When it comes to compilers, the code does not use any compiler-specific thing, yet it has only been tested with GCC.
We are using Mercurial as our SCM.
NASPRO core, NASPRO bridges and Permafrost code can be found in the main repository: http://hg.atheme.org/naspro/.
FreeADSP is in a different separate repository at the moment: http://hg.atheme.org/users/daste/freeadsp/, as well as the zanga-plugins: http://hg.atheme.org/users/daste/zanga-plugins and Tiano: http://hg.atheme.org/users/daste/tiano.
For bug reporting and feature requests use our bugtracker.
There is a development mailing list (mostly deserted at the moment of writing) here: http://www.freelists.org/list/naspro-devel.