Browsing the web for some opensource miningpools I stumbled upon these:
MPOS - Mining Portal Open Source.
https://github.com/MPOS/php-mpos
CK Pool code
https://bitbucket.org/ckolivas/ckpool
NOMP
https://github.com/zone117x/node-open-mining-portal
Thread was from 2-3 years ago though so may not be the best options.