Sorry, you are correct PLS is not open source, but it is free. The license does however read as follows.
2. License Grant. AOL hereby grants You a world-wide, royalty-free, non-exclusive license (a) to use, reproduce, sublicense and distribute the Licensed Software, including as part of one or more Integrated Works; (b) to provide support and maintenance to a third-party in the use of the Licensed Software and in the development and use of one or more Integrated Works; and (c) to use, reproduce, sublicense and distribute the Documentation in connection with all of the foregoing. Perl scripts incorporated with the Licensed Software may be used and modified to facilitate use of the Licensed Software or Integrated Works.
It may not be open source, but free is still free.
Thanks
Mark Rohn