Owncloud update LDAP 50 user cap

I have a question regarding the Owncloud community edition:

Our owncloud is on a very old version 10.0.10 and I wanted to update it.
I found out from a colleague that he didn’t do this update back then because the LDAP sync would have been subject to a charge. In the central.owncloud forum I then found a post that denies this, as the standard version is probably the community edition only without support from Owncloud directly. Only the topic with the 50 users made me wonder.

Here is the post: t/more-than-50-ldap-users-no-longer-open-source/22990
I can’t quite make sense of this post, hence this post.

Can I simply update to a current version (10.13.4) to close the security gaps and will this then remain free of charge or do I have a problem because I have more than 50 users who would be affected by the LDAP Synch?
Many thanks for your help!

Please upgrade to 10.13.4 ASAP. Your version is subject to severe security vulnerabilities.
The information in the post was clarified right away.
You might want to consider looking into ownCloud Infinite Scale for your future needs after the Upgrade above.