The OVAL Checker is just a set of schematron rules that you run against your OVAL Definition to check for common mistakes and conformance to accepted content authoring conventions. It does not have a java wrapper application like OVAL Splitter or OVAL Merge which is why it doesn't have any source code. Are you running into issues with it because you do not have a way to apply the schematron rules to your OVAL Definitions?
Also, you may find the following links about schematron validation and OVAL Definitions content authoring guidelines helpful.
The OVAL Checker is just a set of schematron rules that you run against your OVAL Definition to check for common mistakes and conformance to accepted content authoring conventions. It does not have a java wrapper application like OVAL Splitter or OVAL Merge which is why it doesn't have any source code. Are you running into issues with it because you do not have a way to apply the schematron rules to your OVAL Definitions?
Also, you may find the following links about schematron validation and OVAL Definitions content authoring guidelines helpful.
http://oval.mitre.org/language/about/validating.html
http://oval.mitre.org/repository/about/style.html