A quick example demonstrating how unpacking logic for an asset store package could be set up to be contingent on the presence of a specific code dependency.

DependencyInstall.cs

foreach (Assembly assembly in AppDomain.CurrentDomain.GetAssemblies ())
{
	string location = Path.GetDirectoryName (assembly.CodeBase).Replace (Path.DirectorySeparatorChar, '/');
	
	if (location.StartsWith ("file:"))
	{
		location = location.Substring ("file:".Length);
	}

	if (!location.BeginsWith (Application.dataPath.Substring (0, Application.dataPath.Length - "Assets".Length)))
	// Only search assemblies present in this project (including those resulting from user script compilation)
	{
		continue;
	}

	Type
		solutionAtype = assembly.GetType ("SolutionAType"),
		solutionBtype = assembly.GetType ("SolutionB.Type"); // Remembering to specify namespaces if relevant

	if (solutionAtype != null)
	{
		InstallForSolutionA ();
		break;
	}
	else if (solutionBtype != null)
	{
		InstallForSolutionB ();
		break;
	}
}