Hi again,
I think it is time to provide an update to the list with regards to Gerbil, as I have ported a number of libraries (more are coming), and it now has a nicer README.md you can read formatted on github.
Fundamentally, Gerbil is a new dialect, but it is Scheme after all. It sits on top of Gambit and provides its own macro and module system.
From a Gambit user's perspective, it can be thought of as a macro
expander for Gambit, a module system for Gambit, and (as I am porting more of them) at the end of the day as batteries for Gambit. Macroscopically (pun intended) it brings feature parity in terms of capabilities between Gambit and PLT.
At this point, I can encourage more gambiteers to take a look, as your input can guide libraries and features going forward. Documentation is still very terse, but you can start with src/prelude/core.ss which defines the core language that you get by default in the interpreter and compiler.
The source code is on Github: https://github.com/vyzo/gerbil
It builds on linux and should build on all other unix-like systems. To build, $ cd gerbil && ./build.sh
It takes a while to build, as this does a full stage2 bootstrap: starting from pre-compiled scheme sources, it first uses them to compile itself into the stage1 system and then does a full build with the newly build sources.
Let me know if you have any problems building, and any patches (and feature requests/whish list) are welcome!
-- vyzo