Foreword: you will need 7-zip to extract .tar.xz archives from this site. All archives contain a 32-bit Windows binary, 64-bit Linux/GTK+ binary, and full source code. You may optionally compile the software for 32-bit or 64-bit Windows, OS X or Linux.
bass is a multi-target, table-based, patching-oriented cross-assembler.
beat is a delta-based binary differencing tool. It produces file-based BPS patches, and folder-based BPM patches.
mosaic is a graphical tile editor based on flexible tile definitions. It can also be used on the command-line. With mosaic, you design a tile definition, export the tiles to a bitmap, edit the bitmap in your favorite editor, and then insert it back with mosaic.