I have played around 80 compo games by now and four of them didn’t have a link to the source code. The rules state that: http://www.ludumdare.com/compo/rules/
Competition Rules and Eligibility
Ludum Dare Competition rules are stricter than the Jam rules. This is to encourage a fairer playing field for participants. The core rules are:
- You must work alone (solo).
- All game code and content must be created within the 48 hours. **
- Games must be based on the theme.
- All publicly available libraries and middleware are allowed.
- All content creation, and development tools are allowed. (3dsmax, Photoshop, Flash, etc)
- Source code must be included.