Yes, it was the last OpenGOO v1.6.4.2 unreleased code that got migrated to the FengOffice v1.6.2 as the first in their commercial licencing version where slowly the best plugins were made available to commercial users only.
Study the differences between the FO v1.7.2 and the same version released by the gelsheet.org team with the gelsheet plugin incorporated and we can see that the gelsheet in it's earlier version was commented out in the fengoffice release.
The difference set is available at:
www . apmuthu.com/bugfixes/fengoffice_v1.7.2_to_gelsheet_v1.0.3_diffs.zip
and available to anyone who wants to implement an open source gelsheet plugin for the community is welcome to do so.