The YASEP is a microprocessor "soft core" that is being written in VHDL. It is a small configurable RISCy architecture (16-bit or 32-bit wide) with orthogonal instructions and 16 registers.
The project revolves around a website that depends on Mozilla's JavaScript engine and is designed for casual interactive use by non-specialists. It contains not only the source code but also the documentation and the tools to design, configure and develop the core, as well as the software running on the YASEP.
The files are shared according to the GNU Affero GPL license. The site hosted by TuxFamily is a miror of http://yasep.org/ which is updated several times a year.