Libraries included in SDCC should have a license at least as liberal as the GPLv2+LE. Exception are pic device libraries and header files which are derived from Microchip header (.inc) and linker script (.lkr) files. Microchip requires that The header files should state that they are only to be used with authentic Microchip devices which makes them incompatible with GPL.
If you have ported some library or want to share experience about some code which f.e. falls into any of these categories Busses (I3#3C, CAN, Ethernet, Profibus, Modbus, USB, SPI, JTAG ...), Media (IDE, Memory cards, eeprom, flash...), En-/Decryption, Remote debugging, Realtime kernel, Keyboard, LCD, RTC, FPGA, PID then the sdcc-user mailing list http://sourceforge.net/p/sdcc/mailman/sdcc-user/would certainly like to hear about it.
Programmers coding for embedded systems are not especially famous for being enthusiastic, so don't expect a big hurray but as the mailing list is searchable these references are very valuable. Let's help to create a climate where information is shared.