Assuming that you are writing this package on top of the OpenACS and is statically linked (that is it requires the OpenACS to run):
Steve, if this is an internal package that never gets distributed, then no - it's your package and you do not need to release it.
If, however, you distribute it - sell it or give it - you must pass on the source code and give the receiver all the rights that you have over the code.
talli