SR3C is a small and simple MIT-licensed compression library
(~28KB of source code, no external dependencies), which
nevertheless can compress data with the quality of gzip -7.
the drawbacks are:
• it requires ~4.5MB of RAM for compression or decompression;
• decompression speed is much slower than gzip's;
• compression speed is slower too (yet this case can be improved
by using gdc/ldc to build the code).
usage sample can be seen here.