With 3.5.0-rc1 after installing, configuring with no database (focr_enable_image_hashing is commented out, but the same if "focr_enable_image_hashing 2" is used) the package doesn't pass a lint test:
$ spamassassin --lint
[3932] warn: plugin: failed to parse plugin /etc/mail/spamassassin/FuzzyOcr.pm: Can't locate DBI.pm in @INC (@INC contains: .. /etc/mail/spamassassin /usr/lib/perl5/site_perl/5.8/cygwin /usr/lib/perl5/site_perl/5.8 /usr/lib/perl5/5.8/cygwin /usr/lib/perl5/5.8 /usr/lib/perl5/vendor_perl/5.8/cygwin /usr/lib/perl5/vendor_perl/5.8) at /etc/mail/spamassassin/FuzzyOcr/Config.pm line 161.
...
The problem is that Config.pm look unconditionally for DBI, it shouldn't if the configuration doesn't use MySQL.