Obsidium is described as 'feature-rich professional software protection and licensing system that was designed as a cost effective and easy to implement, yet reliable and non-invasive way to protect your 32- and 64-bit Windows software applications and games' and is an app in the security & privacy category. There are four alternatives to Obsidium for a variety of platforms, including Windows, Windows Mobile, Windows Phone,.NET Framework and Linux. The best alternative is LM-X License Manager. It's not free, so if you're looking for a free alternative, you could try Habanero Simple Software Licensing. Other great apps like Obsidium are LockBytes and CryptoLicensing For .Net.
CryptoLicensing for .Net is a 100% .Net solution to add licensing, copy-protection, activation and hardware-locking capabilities to your .Net, Windows Forms, WPF, Silverlight, Windows Phone 7, Compact Framework, Xbox and XNA apps and libraries and ASP.Net web sites.