It's a reasonable question, but frequently it's quite a complex answer. Given you are likely just one of many applicants I think it may just accelerate most employers turning you down.
If seeing the codebase is an important part of your decision (ie not just knowing what stack/libraries are in use) you may wish to apply for an open source oriented company.
If seeing the codebase is an important part of your decision (ie not just knowing what stack/libraries are in use) you may wish to apply for an open source oriented company.