“Cistron should be excluded from consideration because its LGPL license, which will bring troubles on iOS platform.”
How will this bring trouble in iOS? The LGPL license is for both proprietary and free/open source. The ordinary GPL limits a library’s use for just free programs, not the LGPL.
“The GNU Project has two principal licenses to use for libraries. One is the GNU Lesser GPL; the other is the ordinary GNU GPL. The choice of license makes a big difference: using the Lesser GPL permits use of the library in proprietary programs; using the ordinary GPL for a library makes it available only for free programs.”