simple proof of concept to generate permutations from two lists ... First, there needed to be every permutation for the platforms list. Second was a permutation of the platform and tags lists.

program.cs

using System;
using System.Linq;
using System.Collections.Generic;

namespace Permutations
{
  class MainClass
	{
		public static void Main (string[] args)
		{
			var m = new Model
			{
				Tags = new List<string> {"Graphics", "UI", "Data", "Another" },
				Platforms = new List<string>{"Android", "iOS", "Mac", "windows-rt", "windows-8"}
			};

			for (int i = 0; i < 200; i++) {
				m.Tags.Add (i.ToString());
			}

			HashSet<string> covered = new HashSet<string> ();
			var list = m.Platforms;


			Dictionary<string, int> originalSort = new Dictionary<string, int> ();
			for (int i = 0; i < list.Count; i++) originalSort.Add (list [i], i);


			GeneratePermutations (covered, list, originalSort);

			// This generates the platform/tag permutations
			var query = from tag in m.Tags
				join plat in m.Platforms on true equals true
					select new { Platform = plat, Tag = tag };

			foreach (var i in query) {
				Console.WriteLine ("{0} - {1}", i.Platform, i.Tag);
			}

			Console.WriteLine ("\n\tDone displaying {0} platforms and {1} tags for a total of {2} entries", m.Platforms.Count, m.Tags.Count, m.Platforms.Count * m.Tags.Count);
		}

		static void GeneratePermutations (HashSet<string> covered, List<string> list, Dictionary<string, int> originalSort, int start=0)
		{
			int origCount = list.Count;
			for (int i = 0; i < origCount; i++) {
				var current = list [i];
				for (int y = start; y < origCount; y++) {
					var append = list [y];
					var newEntry = string.Concat (current, ",", append);

					// sort
					newEntry = string.Join(",", newEntry.Split (',')
						.OrderBy (s => originalSort [s])
						.ToArray());

					var currentSet = new HashSet<string> (current.Split (','));
					var appendSet = new HashSet<string> (append.Split (','));
					if (   y > i 
					    && current != append 
					    && !currentSet.Overlaps(appendSet)
					    && !covered.Contains (newEntry) // makes sure we haven't added it already
					    ) {
						list.Add (newEntry);
						covered.Add (newEntry);
					}
				}
			}

			if (origCount < list.Count) {
				GeneratePermutations (covered, list, originalSort, origCount);
			}
		}
	}

	public class Model
	{
		public List<string> Tags;
		public List<string> Platforms;
	}
}