Baculator is a Reverse Polish Notation (RPN) calculator program with an infinite scrollable stack and support for most common mathematical operations as well as some more esoteric operations. Available for Unix/Gtk+, Mac OS X, and MS Windows.
Simple but advanced disc burning for Mac OS X
Create data discs with advanced data settings. Create video and audio discs, Burn will convert if needed. Create DVD-Video discs. Recreate discs. Burn doesn't reinvent the wheel, it uses many powerful open source Unix utilities and is also open source.
Boot OS X, Windows, and Linux on Mac or PC with UEFI or BIOS firmware
If you are unable to configure correctly, have discovered a bug or wish to request a feature, please visit http://www.insanelymac.com/forum/forum/327-clover/, https://sourceforge.net/p/cloverefiboot/discussion/ or open a bug ticket at https://sourceforge.net/p/cloverefiboot/tickets/ for help.
Mac Port Editor
Gamma Studio became Porting Center. http://portingkit.com/
A MacOS X Instant Messaging client to GTalk network, with chat and audio.
PDFView is a simple, yet powerful, Mac Os X PDF viewer, with advanced integration with LaTeX.
Mac Port Editor and WSI Creator
With Porting Center, you can edit any kind of Mac Port for Windows Software which uses Wineskin, CXZ, CXEx and oldest versions of them. With Porting Center unique design, you won't even need to understand how Wine works. Furthermore, with a license, you can export the Port like a WSI file, a file with less than 2Mb of size which contains all the needed information to recreate the mentioned port. After this, the WSI file can be transformed again into a replica of the original port using Porting Kit, a software distributed by Paul The Tall. http://portingkit.com/
Free flexible open source todo manager featuring hierarchical tasks
Task Coach - Your friendly task manager. Task Coach is a free open source todo manager. It grew out of frustration about other programs not handling composite tasks well. In addition to flexible composite tasks, Task Coach has grown to include prerequisites, prioritizing, effort tracking, category tags, budgets, notes, and many other features. However, users are not forced to use all these features; Task Coach can be as simple or complex as you need it to be. Task Coach is available for Windows, Mac OS X, and GNU/Linux; and there is a companion iOS app.
An open source Mac OSX RSS reader with support for RSS/Atom feeds
Vienna is an open source Mac OSX RSS reader with support for RSS/Atom feeds, article storage and management via a SQLite database, written in Objective-C and Cocoa. Feeds can be accessed directly, or through a syncing service supporting the Open Reader API, like BazQux.com, FeedHQ.org, InoReader.com or TheOldReader.com. Development now happens on GitHub: https://github.com/ViennaRSS/vienna-rss
OpenSource Mac OS X project to create simple Application that will communicate via AppleScript and Cocoa with Macintosh applications and iChat A/V 2.0. It is in Brazilian Portuguese and English.