There are several levels of support for DVD. The BeOS is capable of reading from ordinary CD-ROMs and DVD disks which are formatted with a BeOS-compatible file system (for example, BFS or ISO 9660).
Support for special, DVD-specific file systems such as UDF is not currently available for the BeOS, but it should simply be a matter of writing a file system add-on to support the specialized file system(s).
BeOS Release 4 will have writable ATAPI support, and the ability to read DVDs. However, we are not planning to support DVD encoding in Release 4, i.e. the ability to play encoded movies. That's tentatively on the Release 5 list.