Forum OpenACS Q&A: Response to having problems with the installing openacs4
That's right. nsssl.so = 128-bit "U.S. domestic-grade" encryption. nsssle.so = 40-bit "export-grade" encryption (hence the 'e' suffix). I guess the export version of the module is being included in some binary distributions (it's been such a long time since I personally downloaded a binary distribution).
The SSL modules (nsssl.so, nsssle.so, or nsopenssl.so) are recommended for A.) administrative purposes, and possibly B.) for e-commerce. They're basically used if you want/need HTTPS.
nsssl.so and nsssle.so only support the SSLv2 protocol. Scott's nsopenssl.so module supports SSLv2, SSLv3, and TLSv1. In addition, Scott continues to work on nsopenssl, adding more support for client verification, etc. It appears that no work has been done on the AOLserver nsssl(e) module for a couple of years (e.g., not even SSLv3 nor TLSv1).