OnStartup.cs

using System;
using System.IO;
using System.Reflection;
using ICVT.JPEGMini.Common;

namespace JpegMini.Crack.Runtime
{
    public static class OnStartup
    {
        public static void Run()
        {
            try
            {
                ActivationManager a = ActivationManager.Current;
                a.DailyLimitChanged += OnDailyLimitChanged;

                OnDailyLimitChanged(0);
            }
            catch (Exception e)
            {
                File.WriteAllText("injected_exception.txt", e.ToString());
            }
        }

        static void OnDailyLimitChanged(int v)
        {
            try
            {
                ActivationManager a = ActivationManager.Current;
                if (a == null)
                    throw new Exception("a is null");

                MethodInfo m = a.GetType()
                                .GetProperty("RemindedDailyLimit")
                                .GetSetMethod(true);

                if (m == null)
                    throw new Exception("m is null");

                m.Invoke(a, new object[] { 99 });
            }
            catch (Exception e)
            {
                File.WriteAllText("injected_exception2.txt", e.ToString());
            }
        }
    }
}

Program.cs

using System;
using System.Linq;
using System.Reflection;
using Mono.Cecil;
using Mono.Cecil.Cil;
using Mono.Collections.Generic;

namespace JpegMini.Crack
{
    class Program
    {
        static void Injected()
        {
            Assembly.Load("JpegMini.Crack.Runtime")
                    .GetType("JpegMini.Crack.Runtime.OnStartup")
                    .GetMethod("Run")
                    .Invoke(null, null);
        }

        static void Main()
        {
            AssemblyDefinition a = AssemblyDefinition.ReadAssembly("log4net.dll");

            MethodDefinition cctor = a.MainModule.GetType("log4net.LogManager").Methods.Single(m => m.Name == ".cctor");

            Collection<Instruction> insns = cctor.Body.Instructions;
            int last = insns.Count - 1;
            if (insns[last].OpCode != OpCodes.Ret)
                throw new InvalidOperationException();

            insns.RemoveAt(last);

            string injectedName = new Action(Injected).Method.Name;

            Collection<Instruction> injected =
                AssemblyDefinition.ReadAssembly("JpegMini.Crack.exe")
                              .MainModule.GetType(typeof(Program).FullName)
                              .Methods
                              .Single(m => m.Name == injectedName)
                              .Body.Instructions;

            foreach (Instruction insn in injected)
            {
                if (insn.OpCode == OpCodes.Call || insn.OpCode == OpCodes.Callvirt)
                {
                    MethodReference op = (MethodReference)insn.Operand;
                    insn.Operand = a.MainModule.Import(op);
                }
                insns.Add(insn);
            }

            a.Write("log4net.injected.dll");
        }
    }
}