Not sure what you mean by 'Apple devices'. It certainly works fine on any OS X device. It doesn't work on iOS devices as yet, nor on windows mobile devices. On desktop/laptop systems, webGL works fine for Chrome, Firefox, Safari, and Opera, but not for Internet Explorer. On mobile devices, it works for Firefox, Chrome and Opera on Android. See codeflow.org/entries/2013/feb/02/why-you-should-use-webgl/#does-it-run-on-my-favorite-platform.
I think you can expect it to come to iOS though, because Apple does support open HTML5 technologies (in preference to proprietory technologies, such as Adobe Flash) and does support OpenGL ES on iOS (and OpenGL on OS X).
For things like this - open source projects - you generally get them faster on open source operating systems, such as Linux, FreeBSD, and Android. For the latter, the downside is that you get reduced security (there are no viruses for OS X or iOS, nor very likely to be).