merge.py

#!/usr/bin/env python3
# -*- coding: utf-8 -*-

import csv

with open('data.csv') as f:
    reader = csv.reader(f, delimiter=';', quotechar='"')
    rows = [x for x in reader][1:]

c = {}

for r in rows:
    if not r[1]:
        continue
    kod = r[0]
    if not kod in c:
        c[kod] = []
    c[kod].append(r[1])

for k in c.keys():
    c[k] = ' | '.join(c[k])

with open('data2.csv', 'w') as f:
    writer = csv.writer(f, delimiter=';', quotechar='"', 
                        quoting=csv.QUOTE_MINIMAL)
    writer.writerow(['tin', 'founders'])
    writer.writerows(c.items())